A food allergy causes a specific immunological reaction in the body that can be observed and diagnosed by various tests. An immunological reaction is a reaction against foreign molecules entering the body; normally, its purpose is to protect the body. In the case of food allergy, this reaction is extreme and is provoked by foods that have no adverse effects on most people. These adverse reactions are immediate and localised; common sites are the mouth (swelling of the lips), digestive tract, the airways (wheezing and breathing problems) and the skin .